Some interesting changes with 10.1. Regarding the proxy workflow, in the past you could cheat the system and generate proxies externally, such as with Resolve. If you placed them in the correct folder, FCP X would toggle back and forth. Now it seems that X will only see proxy files generated by X.
On the plus side, relinking now seems more relaxed in 10.1. I tested a set of files, where I have camera originals, plus edit proxies with LUT/burn. Name, TC, reel/source ID and length all match. FCP X lets me freely relink back and forth between these two sets, like in FCP 7.
Thanks for that, Oliver. I remember reading about the proxy workflow when you were testing this out on your last project.
One thing I noted is that if you allow FCP to manage the media, and you relink to a different file, then FCP will trash the original media. If FCP doesn't manage the media (it resides outside the library) then the old clips remain in their location.